Lithium-ion secondary batteries are mainstream commercial products and are presently being developed to have lighter weight, higher energy capacity, a longer life span, and better safety. However, the non-aqueous electrolyte solution used in commercial batteries is prone to leakage and explosion, and thus is dangerous. Also, the dendrite present on the negative electrode of the batteries may lead to short circuits or even explosions. Further improvements are required to ensure the safety of the non-aqueous electrolyte solution for daily applications. On the other hand, polymer gel electrolyte has been developed as a safer alternative for the non-aqueous electrolyte solution. However, due to the high viscosity of the polymerized gel electrolyte, it is unlikely to use a vacuum filling process to fill the electrolyte for battery fabrication, which becomes a fabrication bottleneck. In addition, the relatively low conductivity of the conventional gel electrolyte is another problem that should be solved.